Hard Chrome Plating needs more Salt Spray Test hours

adv.

A discussion started in
2007 & continuing through 2017 . . .

(2007)

Q. We have a mechanical assembly used for outdoor applications. Base material is Mild Steel. Operations are press work and machining. It is hard chrome plated to 10 to 15 microns. Could anyone help to know how many hours of salt spray test it would with stand. Suggestions for alternates are welcome. The application is commercial so cost is a big factor. Plating should withstand at least 100 to 120 hours of salt spray for corrosion resistance.

Krishnan R manufacturer - Bangalore, India

(2007)

A. Check your trivalent status in chrome bath that should be less than
6 gm./ltr. Second increase the no. of microcracks on the job more than 400 cracks/linear cm.

A. Hi Chandra. I think it's borderline possible -- but carefully re-engineering a plating process to attempt to pass a wrong and non-informative accelerated corrosion test doesn't seem like a very productive path to follow :-)

The thing is, real-world corrosion is a complex phenomena and we think that, for the case of nickel-chrome plating, the standard ASTM B117 [link by ed. to spec at TechStreet]
salt spray test is rather non-informative because it poorly imitates real-life. CASS and Corrodkote tests seem to more accurately predict the life of nickel-chrome coatings.

I think what you might want to do is decide what life you need under what real-world conditions, and then try to design an accelerated corrosion test that will be helpful towards predicting whether the parts will pass the real-world needs. Good luck.

Regards,

Ted Mooney, P.E. RETfinishing.comPine Beach, New Jersey

September 6, 2013

A. ASTM B456 [link by ed. to spec at TechStreet] has the specification for nickel/chrome plating corrosion resistance. It lists the thickness needed and how many hours the plating will survive various tests.

Jim Treglio - Vista, California

Second of two simultaneous letters -- September 7, 2013

Q. My question is simple what process to be adopted by us to achieve 500 hours salt spray test (CASS) on ms seamless pipe having OD 219 mm, Length 1070 mm by duplex nickel hard chrome plating?
How much coating thickness is needed for this test.

Anyone help my ??

Chandra Prakash- Noida U.P. India

October 17, 2013

A. Hard chrome is a poor corrosion protector. It only gives approx. 48 hours in NSST.

Sara Michaelichemical process supplier
Tel-Aviv, Israel

October 22, 2013

A. Hi Chandra,

500 hours of a CASS is quite a challenge for any coating! I guess if it was me I'd go with about 75 microns of nickel undercoat followed by chrome to the finish size, but would probably want somewhere around 100-150 microns as a minimum.

I'm not going to guarantee that it will work, but it is a starting point.

Brian Terry aerospace - Yeovil, Somerset, United Kingdom

October 23, 2013

A. Hi,

The only way to receive 500 hours in a salt spray test for chromium is to pulse plate the chrome.

Regards

Anders Sundman3rd Generation in Plating
Consultant - Arvika, Sweden

Need Nickel-chrome plating to survive 500 hour CASS test

May 8, 2014

Q. My question is simple what process to be adopted by us to achieve 500 hours salt spray test (CASS) on ms seamless pipe having OD 219 mm, Length 1070 mm by duplex nickel hard chrome plating?
How much coating thickness is needed for this test.

Anyone help me?

Chandra Prakash- Noida, U.P. INDIA

May 2014

Hi Chandra. This is the 4th time you've asked your "simple question" on this page, and you also asked it on letter 54204.

Please try to PARTICIPATE in the discussion, phrasing your on-going questions in terms of the many answers that have already been offered, so we can keep moving forward. Instead of thanking people, you've ignored them while posting the same question, insisting that it is simple to answer :-(
It is probably wearing out their patience ... I know it wore out mine :-)

Regards,

Ted Mooney, P.E. RETfinishing.comPine Beach, New Jersey

May 10, 2014

A. Dear Sir,

500 hrs of CASS life for nickel plated MS pipe seems very difficult to achieve. Kindly favor with end application details. This can help us in understanding the need for such high performance from the coating.

Even for automotive tubular components such as Two wheeler handles, which are exposed to most severe (Grade 4) of outdoor atmospheric conditions under high intensity motion such high CASS life is not specified. It may be Neutral Salt spray test life. Please Confirm.

Regards,

Dilip Thakur - Mumbai India

December 2, 2015

Q. We require hard chrome plating with 10 to 15 microns to be withstand min. 76 hrs salt spray test coated on MS plate, as we have tried the test result is 46 hours only, then red rust is appeared. Please suggest alternate process but finish and wear resistance should be equal to hard chrome. Already we have tried Zinc-nickel coating, found satisfied on salt spray test -- but our client needs only hard chrome finish. Anyone can suggest please?

P gunasekaran - Coimbatore, Tamil Nadu, India

December 2015

A. Hi. I am not familiar with the pulse plating which Anders describes, but you could ask him for more info.

Have you considered nickel plating under the hard chrome?

Regards,

Ted Mooney, P.E. RETfinishing.comPine Beach, New Jersey

December 4, 2015

A. Hi, I would not expect any real corrosion resistance from hard chrome plating to that thickness. Hard chrome is micro-cracked, due to the stresses in the coating, this means the base material can be attacked with relatively thin coatings of chrome. You either need to look at different technologies (e.g. thin dense chrome, which is not micro-cracked) or you need an undercoat as Ted has suggested (nickel or copper will serve your purposes, although nickel is the usual standard)

Brian TerryAerospace - Yeovil, Somerset, UK

December 7, 2015

A. Hi,
A combination with electroless nickel and hardcrome will give you more than 75 hour in salt spray test. But is a little difficult to activate the EN; to do the activation must be in a acid which contains sulphuric acid and hydrofluoric acid. The detail must be cathodic in activation.

Hi,
If anyone who plates hard chrome is interested about pulse plating with hard chrome, I can help you serious about it. We tested the plating in a salt chamber, after 500 hours no corrosion. So I know pulse plating works great.

Q. Hi,
We are hard chrome plating on machined 270 mm OD ERW tubes, the issue rises when we get pin holes and minor cracks in the raw material as it gets rusted in salt spray chamber at 30 to 35 hours. Is there any particular standard describing the salt spray spec for hard chrome plating? What shall I do when we find pin holes in which hard chrome plating doesn't deposit? Kindly help me with this situation.

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